This invention involves a multi-ply ribbon ink cartridge for use in impact pin printers. More particularly the invention involves the use of this cartridge in point of sale printers.
The use of compact and larger printers to print receipts, credit card vouchers and other printed matter at point of sale locations has proliferated to a point where almost every retail outlet has a point of sale printer. For example, at supermarkets and other large retail outlets, the computer driven check out apparatus includes a dot matrix printer that can print a record receipt of the purchases as well as coupons for future purchases. At the same type of location, it is common to have a small impact printer to print a credit card voucher which shows the total purchase amount and provides for signature by the customer. This latter type of device is now commonly used in filling stations and other retail outlets to facilitate credit card purchasing. Automated bank tellers utilize a small printer to print out the receipt and the balance information on the account of the customer. These printers are commonly nine pin, impact dot matrix printers that have a speed less than about 200 characters per second. Some printers are line printers wherein the pins are aligned across the length of the printing space and operate at a speed of about 120 to about 240 lines per minute. This speed is slower than most computer printers used for personal use and much slower than the commercial type printers used for professional offices and the like.
The point of sale printers, both line and serial types, utilize a replaceable printer ink cartridge to supply the ink during the printing process. While these ink cartridges vary widely in size, shape and configuration, they all include a number of common elements. The ink cartridge includes a housing with an exterior wall structure that encloses an internal chamber. First and second openings are provided through the wall structure both opening to the internal chamber. Generally these openings are on opposite ends of the internal chamber. An endless ribbon is installed in the cartridge with almost the entire length of the ribbon in the internal chamber. A short section of the ribbon trained out of the first opening and back into the internal chamber through the second opening. A guide mechanism is provided to guide the section of the ribbon on the outside of the chamber along a path from the first opening to the second opening. The cartridge is also equipped with a moving mechanism that is responsive to an external rotative force provided by the printer to pull the ribbon out of the internal chamber through the first opening along the guide mechanism and back into the second opening while pushing the ribbon back into the internal chamber. Ink is absorbed onto the endless ribbon. A visible mark on the paper results when the path of the external section of the ribbon is interposed between the paper and the pins to provide an impact on the ribbon against the paper.
The ribbons on the point of sale printer ink cartridges, as well as those for the higher speed printers, are essentially all a single ply of nylon fabric. The nylon fabric may be woven from threads that are textured, flat, twisted and the like. Nylon is the fiber of choice as the structure life of the ribbon is an important if not critical requirement of the ink cartridge. In this case the term "life" is referring to the time before the ribbon wears out and breaks causing a complete failure of the printer or frays on the surface to a degree that it interferes with the printing. It is most important that the structure life of the ribbon be longer than the life of the ink adsorbed on the ribbon.
While print quality is important in point of sale printing units, the life of the ink supply on the ribbon is even more important. Nylon, chosen for its durability, does not have a high level of ink absorption capability. In normal production operations, it is difficult to attain ink loading on the single ply of nylon fabric higher than about 20% of the weight of the ribbon. This limit places a definite life of the ink supply before the ribbon cartridge must be replaced.
It is common to observe poor print quality with extremely light printing on point of sale printers. It is so common that almost everyone has received an apology from the sales clerk as to the quality of the print out being handed to them at the check out location. From a practical stand point, the ink ribbon cartridges on point of sale printers are commonly used well beyond the recommended period of use. Some companies are offering services to regularly maintain the point of sale equipment despite the high costs of such procedures. In general, the life of the ink supply is the determining factor as to when the printer requires a change of the ribbon cartridge.
Despite the long felt need of printer ink cartridge with an extended printing life, no substantial improvements to this life have been achieved. In U.S. Pat. No. 2,728,439, a typewriter ribbon of two ply of nylon fabric is described indicating that this ribbon will last in use far longer under severe service conditions than the ribbons of the then prior art. In Japanese Application No. 57-105179 a ribbon for typewriters and printers is described constructed of two porous organic films with printing ink enclosed between the two films. Printer ribbon substrates are described in U.S. Pat. No. 4,016,321 and impression fabric made of yarn containing variable shrinkage filaments for use in an inking ribbon is described in U.S. Pat. No. 3,749,222. Despite this prior art, a great need to extend the life of the point of sale printers has not been achieved. Further, the objects described herein below have not been attained by the prior art.